The present invention relates to a method and system for recovering free product from a groundwater well while minimizing the removal of groundwater from the well.
Groundwater contamination, typically arising from petroleum storage tank spills or from intentional or accidental discharge of liquid hydrocarbons or compositions containing same, has become a problem of increasing concern. This type of contamination occurs not only at industrial complexes, but also in suburban neighborhoods, which would appear to be havens from such phenomena. The source of contamination in suburban neighborhoods or areas is very commonly automobile service station sites at which antiquated or abandoned storage tanks have released gasoline, fuel oils, lubricants, and the like into the local groundwater. Other common sources of such noxious materials can include dry cleaning establishments and/or manufacturers or distributors of the tetrachloroethane which is used in the dry cleaning process.
Various remediation techniques have been utilized in the past for the treatment of contaminated groundwater in order to reduce or eliminate the contaminants, such as COCs. One of the most widely used systems is one based on so-called xe2x80x9cpump and treatxe2x80x9d technology. These systems withdraw the contaminated groundwater and a phase-separated product from a recovery well located in the groundwater and pump it to an above ground treatment facility. Thereafter, various treatment techniques, as are well known, are used to remove contaminants from the displaced groundwater. These xe2x80x9cpump and treatxe2x80x9d systems are relatively expensive to install and require that the remaining contaminants, which have been separated from the groundwater, be disposed in an environmentally friendly manner. These processes further increase the cost of the techniques.
One example of a known remediation system is disclosed in U.S. Pat. No. 5,286,141. The ""141 patent teaches oxidizing the source of groundwater contamination to harmless constituents by locating a plurality of mutually spaced wells into a groundwater region. A treating flow of hydrogen peroxide solution is provided into the groundwater from one or more wells. The treating flow typically contains reaction surface enhancing reagents, which provide increased surfaces at which the reaction between the hydrogen peroxide and the hydrocarbon contaminants may occur. Further, a catalytic agent is also preferably incorporated into the treating solution or as a pre-injection into the groundwater region to promote the desired reaction between the hydrogen peroxide and hydrocarbons.
Recently, there has also been increasing interest in bioremediation technology. However, its use in treating groundwater has been relatively ineffective due to the complexity of the procedures and equipment required, including expensive and complex reactors. Moreover, current bioremediation techniques can cause adverse geochemical reactions and can introduce new toxic compounds into the groundwater. Additionally, current bioremediation systems, still require the use of non-organic catalysts or additives to cause the process to be completed in a reasonable period of time. These catalysts or additives raise other contaminant issues with respect to the groundwater.
It is known that naturally growing bacteria in the groundwater can break down groundwater contaminants. However, these bacteria are not always present in large enough quantities to be effective and can also be absent altogether. Moreover, these bacteria feed off oxygen and the lack of oxygen is the single biggest limiting factor on the growth of the bacterial population and therefore contaminant decrease. Ambient air, which is comprised of about 21% percent oxygen, only results in approximately 10-12 ppm of dissolved oxygen in the groundwater and thus is not sufficient to adequately destroy or reduce contaminants. Various attempts to increase the amount of oxygen by utilizing oxygen releasing compounds have been tried, but these oxygen releasing compounds, such as magnesium peroxide or calcium peroxide are expensive. Further, these oxygen releasing compounds only produce a small amount of usable oxygen and therefore do not significantly increase the bacterial population.
In some instances, the remediation of groundwater can be further complicated by large amounts of free product in the area to be remediated. Thus, in addition to the contamination that is present in the groundwater, a thicker contaminant is present on the top surface of the water, which has not yet been dissolved. The existence of the free product can further increase the time required to remediate groundwell water. Thus, it is desirable to remove the free product prior to the step of remediation. One method for the removal of free product requires the removal of free product and groundwater and then separating it above ground at a treatment facility, as discussed above. This typically requires a separate building and holding tank, which are costly and take up considerable space. Moreover, these prior removal methods also remove large amounts of groundwater as there is no real way to distinguish between where the free product ends and where the water begins. These methods are thus both expensive and inefficient.
It is therefore an object of the present invention to provide a method and system for removing increased amounts of free product from a groundwater well prior to groundwater remediation treatment.
It is another object of the present invention to provide a method and system for removing increased amounts of free product from a groundwater well, while minimizing the removal of groundwater.
It is still another object of the present invention to provide a method and system for removing increased amounts of free product from a groundwater well that is less expensive and more efficient than prior removal systems.
It is a further object of the present invention to provide a method and system for removing free product from a groundwater well that is relatively easy and inexpensive to install and operate.
It is yet another object of the present invention to provide a method and system for removing free product from a groundwater well that can be installed with minimal site disturbance.
It is still a further object of the present invention to provide a method and system for removing free product from a groundwater well that can be easily and readily converted to a bioremedial groundwater remediation system.
In accordance with the above and other objects of the present invention a method and system for removing free product from a groundwater well is provided. The method includes determining whether a subterranean body of groundwater is contaminated. If the groundwater is contaminated, it is monitored to determine whether free product that has yet to dissolve into the groundwater is located on the surface thereof. If free product is present, a plurality of extraction points are placed below ground and into communication with the body of groundwater. Each of the plurality of extraction points is positioned to maximize communication with the free product and minimize communication with the groundwater. A vacuum source is placed in communication with each of the plurality of extraction points to remove free product from the well through the extraction points. The flow of fluid removed from the well is periodically monitored to ensure that the extraction points are properly positioned with respect to the surface of the groundwater. The proper position is preferably determined by viewing a clear section of the extraction hose to determine if free product and water is being transported along the extraction hose by xe2x80x9centrained flow.xe2x80x9d Entrained flow is the stream of fluid droplets in high velocity air stream.
The system includes a monitoring well in communication with a subterranean body of groundwater to determine whether any free product exists on the surface of the groundwater as well as to determine the thickness of any free product. A plurality of extraction tubes extend below ground to intersect the free product. Each of the tubes has a first end that is located at a respective extraction point where the tube intersects the free product at a plurality of extraction points. Each of the tubes has a second end that is in communication with a vacuum source to draw free product from the surface of the groundwater. Each of the tubes has a clear portion adjacent the second end that allows the entrained flow stream extracted from the plurality of extraction points to be viewed.
The above objects and other objects, features and advantages of the present invention will be apparent from the following detailed description of best made for carrying out the invention to be taken in connection with the accompanying drawings and appended claims.